PITTSBURGH — Mario Williams might not be the most dynamic, most feared defensive end in the National Football League right now. But he’s getting there.

Certainly, the Steelers know all about him.

When asked what he knows about the Houston Texans, who open the NFL season with a 1 p.m. game Sunday at Pittsburgh’s Heinz Field, Steelers right tackle Willie Colon said, “They got the big gun, Mario Williams.”

The Texans, 8-8 last year, have three No. 1 draft picks on their defensive line. But clearly the main man in Houston right now is a remarkable physical specimen wearing No. 90.

“He’s definitely one of the better defensive ends in the league,” said Marvel Smith, the Steelers’ left tackle. “He possesses a rare skill set. There aren’t too many guys his size with that type of speed and strength. That’s what sets him apart.”

Williams, who’s 6-foot-7 and 291 pounds, became headline news two years ago when he was chosen with the first pick of the 2006 NFL Draft.

The Texans, coming off a 2-14 season, could have chosen Heisman Trophy winner Reggie Bush, the Southern Cal running back. Instead, they shocked the sports world by taking Williams, who turned pro after his junior year at North Carolina State.

Bush went to New Orleans, which had the second overall pick, and helped the Saints reach the NFC Championship Game.

Immediately after drafting Williams, the Texans were roundly criticized for not jumping on Bush. The criticism continued when Williams recorded only 4.5 sacks as a rookie.

But last season, Williams had his breakout year, tying for third in the NFL with 14 sacks. He also forced two fumbles and scored his first pro touchdown by returning a fumble 38 yards.

Even though he’s just 23 years old, he’s already considered the prototype for NFL defensive ends.

“He looks like the first pick in the draft,” Steelers coach Mike Tomlin said. “He’s a talented player … very disruptive, athletic and powerful … this guy is extremely powerful and athletic.

“He runs his line stunts very efficiently. This morning (while watching videotape), I counted four steps he took to get to the quarterback on a tight end stunt. That’s not a lot of time. Somebody’s got to block this guy. That’s what makes him who he is. That’s why they drafted him first overall.”

On the Texans’ depth chart, Williams is listed as the right defensive end. But he also switches to left D-end at times.

That means that Colon will have to block Williams from time to time. But mostly, it’s Smith, a ninth-year pro, who’ll be assigned to Williams. And whether it’s Colon or Smith who lines up across from Williams, they’ll probably need help from a tight end or running back.

“It’s not like this is something new for me,” Smith said. “As a left tackle, I play against some of the best defensive ends in the league every week. Every week, it’s my job to be ready and go out there and do the things I’m supposed to do.”

On Sunday, the key to victory for the Steelers may be keeping Williams from disrupting quarterback Ben Roethlisberger.